This invention relates to the preparation of 2,5-diketogluconic acid.
Heretofore, 2,5-diketogluconic acid has been produced by several different varieties of bacteria such as Acetobacter melanogenum, Acetobacter aurantium, Gluconoacetobacter rubiginosus, Gluconoacetobacter liquifaciens and Pseudomonas sesami. The use of these microorganisms, however, is not satisfactory from an industrial point of view because of relatively low yields of 2,5-diketogluconic acid, relatively long fermentation times and because of the production of large amounts of brown or yellow-brown pigments as by-products of cultivation, thereby decreasing the purity of the desired 2,5-diketogluconic acid.
U.S. Pat. No. 3,790,444 relates to the production of 2,5-diketogluconic acid, without accompanying brown pigment, by a new species designated Acetobacter fragum ATCC No. 21409.
2,5-diketogluconic acid is useful as an intermediate for the preparation of ascorbic acid. A solution of 2,5-diketogluconic acid may be selectively reduced to 2-ketogulonic acid, which may be converted to ascorbic acid. The reduction of 2,5-diketogulonic acid may be effected by reduction with an alkali metal borohydride, as disclosed in U.S. Pat. No. 4,159,990, or by a fermentive reduction as described, for example, in U.S. Pat. Nos. 3,922,194, 3,959,076 and 3,963,574.
2,5-diketogluconic acid is also useful as an intermediate for the preparation of comenic acid by heating in the presence of an acid, as described, for example, in U.S. Pat. No. 3,654,316.